1. Field of the Invention
This invention relates generally to inflatable type modular occupant restraint systems for passenger vehicles or, as it is more commonly known, an air bag restraint system. Such a system may be installed in an automobile or other vehicle, at least in part on the steering wheel for the protection of the driver and also in the dashboard or passenger side instrument panel for passenger protection in the event of a collision. More particularly, this invention relates to an improvement in a means for controlling the initial deployment of the air bag cushion.
2. Description of Related Art
An air bag restraint system module typically includes a canister, which has an open side and encloses an inflator and at least part of an air bag, and a cover which conceals the module from view. When an air bag module is designed for the driver side of a vehicle the module is located in the steering wheel behind a cosmetic cover which is an integral part of the steering wheel design. When the air bag module is designed for the passenger side of a vehicle, the container may be located just behind the vehicle dashboard, cosmetic cover, or passenger side instrument panel (hereinafter referred to as "dashboard") and the cover may form an integral part of the vehicle dashboard.
When the vehicle is involved in a collision, a crash signal initiates operation of the inflator to cause the air bag cushion to deploy. The inflator produces an inert gas (e.g., nitrogen) which is directed under pressure into the air bag cushion to force the air bag cushion out of the container and through the opening provided by rupturable tearseams in the steering wheel cover, or tearseams or a hinged cover in the dashboard, and into the passenger compartment of the vehicle. As the air bag cushion is directed into the passenger compartment, it is inflated by the continued flow of gas produced by the inflator. An untethered driver side air bag cushion deploys to fill the space between the steering wheel and the driver's head and upper torso. On the passenger side the air bag cushion is directed between the windshield and the occupant to fill the space between the windshield and the occupant's head and upper body. During the early stages of the air bag cushion's deployment, it is preferable to expand the air bag cushion between the steering wheel or dashboard of the vehicle and the occupant's torso in order that the momentum of the moving occupant can be initially absorbed from the occupant's torso. After the initial contact the air bag cushion still provides protection to the head and upper body of the occupant during a collision.
Tethers have been used to guide the deployment of an air bag cushion for motor vehicle occupant protection. Air bag cushions are commercially available with tethered driver side and passenger side air bag cushions wherein the tethers are attached by fastener members to the impact absorbing part of the air bag cushion and to the air bag cushion near the gas inlet opening. During high energy collisions a tethered air bag cushion is positioned to receive the initial impact from the vehicle occupant's head and upper torso.